Because this process occurs naturally, it does not matter if a tire is being used, stored as a spare, or simply waiting on a store shelf for an unsuspecting consumer. A 2006 survey showed that only 4% of consumers are aware that tires become more dangerous as they age.

In 1973, the average tread life of a passenger car tire was approximately 24,000 miles. If the tire has only 10 digits, the tire was manufactured before the year 2000. This six-year expiration date begins from the day the tire was manufactured at the plant—not the date it was sold to a consumer or the date that it was installed on a vehicle.

The last two numbers identify the year of manufacture (e.g., a tire with the information "DOT XXXXXXX2714” was manufactured in the 27th week of 2014).